获取当前年月日

LocalDate now = LocalDate.now();                    //2022-12-18
int year = LocalDate.now().getYear();               //2022
int month = LocalDate.now().getMonth().getValue();  //12
int day = LocalDate.now().getDayOfMonth();          //18

获取当前时分秒

LocalTime now = LocalTime.now();           //19:21:55.125
int hour = LocalTime.now().getHour();      //19
int minute = LocalTime.now().getMinute();  //21
int second = LocalTime.now().getSecond();  //55

获取当前年-月-日 时:分:秒

DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime now = LocalDateTime.now();
String nowTime = dtf.format(now);   
System.out.println(dateFormat);     //2022-12-18 19:21:55

日期时间之间格式相互转换

String nowTime = "2022-12-18 19:21:55";
Date date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(nowTime);
String dateFormat = new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒").format(date);
System.out.println(dateFormat);     //2022年12月18日 19时21分55秒